A typical ship-based Radar system will be provided with ship's navigation reference data (course and speed relative to the land) so that the apparent motion of the objects identified by the Radar on the moving ship can be compensated for the motion of the ship.
Under normal operation it may be assumed that reliable and accurate ship's course and speed data is available, but under some circumstances such as fault conditions, this data may not be available or may not be as accurate as would be expected or desired.
As such, there is a desire to improve the quality and accuracy of navigation reference data made available to the Radar.